An indoor unit of an air-conditioning apparatus includes a header main pipe to which an indoor pipe is connected at a brazed portion and header branch pipes. The header branch pipes are connected to first ends of heat-transfer pipes included in an indoor heat exchanger at brazed portions. The indoor pipe is connected to indoor refrigerant branch pipes at brazed portions. The indoor refrigerant branch pipes are connected to second ends of the heat-transfer pipes. A first leaked refrigerant receiver is disposed under the brazed portions. A first temperature sensor is disposed in the first leaked refrigerant receiver. A second leaked refrigerant receiver is disposed under flare joints connecting the indoor pipes to extension pipes, respectively. A second temperature sensor is disposed in the second leaked refrigerant receiver.